Pneumatic tire

Abstract

Pneumatic tire wherein a rubber layer (A) is disposed as an inner liner at an innermost layer side of the tire, and a rubber layer (B) disposed between the above inner liner and a carcass ply layer and adjacent to the above inner liner comprises a rubber composition containing a natural rubber alone or a natural rubber and a synthetic diene rubber as a rubber component, wherein rubber layer (A) contains a butyl rubber alone or a blend rubber of a diene rubber and a specific amount of a butyl rubber as a rubber component; rubber layer (B) contains a bismaleimide compound as a cross-linking agent, sulfur and a vulcanization accelerator; a blend amount of the sulfur and a blend amount of the vulcanization accelerator are modified to specific ranges; and an elongation at break after subjected to air heat aging at 100° C. for 250 hours is 150% or more.

The invention claimed is: 
     
       1. A pneumatic tire in which a rubber layer (A) having an excellent air impermeability is disposed as an inner liner at an innermost layer side of the tire and in which a rubber layer (B) disposed between the inner liner and a carcass ply layer and adjacent to the inner liner comprises a rubber composition containing a natural rubber alone or a natural rubber and a synthetic diene rubber as a rubber component, wherein the rubber layer (A) contains:
 a butyl rubber alone or a blend rubber of a diene rubber and a butyl rubber as a rubber component, and 30 parts by mass or more of the butyl rubber is contained based on 100 parts by mass of the rubber component; the rubber layer (B) is composed of a rubber composition comprising 0.4 to 1.0 parts by mass of sulfur, 1.5 to 3.0 parts by mass of a vulcanization accelerator, and 1.0 part by mass or more of a bismaleimide compound as a cross-linking agent based on 100 parts by mass of the rubber component, and in which a blend amount of the sulfur and a blend amount of the vulcanization accelerator satisfy the following equation (I); and 
 an elongation at break after subjected to air heat aging at 100° C. for 250 hours is 150% or more:
   (vulcanization accelerator)≤(−2.14)×(sulfur)+5.43  (I).
 
 
 
     
     
       2. The pneumatic tire as described in  claim 1 , wherein an elongation at break after subjected to air heat aging at 100° C. for 1000 hours of the rubber composition for the rubber layer (B) is 150% or more. 
     
     
       3. The pneumatic tire as described in  claim 1 , wherein the pneumatic tire is a pneumatic tire for heavy load vehicles. 
     
     
       4. The pneumatic tire as described in  claim 2 , wherein the pneumatic tire is a pneumatic tire for heavy load vehicles. 
     
     
       5. The pneumatic tire as described in  claim 1 , wherein the pneumatic tire is a pneumatic tire for heavy load vehicles having a rim diameter of 25 inches or more.